Of the 529 coal miners killed in major mine disasters between 1951 and 1969 at least 88 died as a result of breathing irrespirable or toxic gas. At present, the only protection from such gases which the coal miner carries is a filter respirator which catalytically converts carbon monoxide to less toxic carbon dioxide. This device is not reliable in carbon monoxide concentrations greater than 2 percent and affords no protection against oxygen-deficient or toxic atmospheres.
A self-contained breathing apparatus which is small and light enough to be kept on or about the miner's person, as is the present carbon monoxide filter respirator, would greatly increase a miner's chance of survival after a fire or explosion. At present, there is no personal breathing apparatus of suitable size and wieght available which is approved by the U.S. Bureau of Mines.
The 1969 Coal Act requires that "each miner shall be provided with a self-rescue device adequate to protect such miner for one hour or longer." The Sunshine Mine disaster in 1972 in which 91 men were killed due to suffocation by smoke or carbon monoxide, reemphasized the need for newer, more reliable self-contained breathing apparatus.
Minimum requirements for a personal breathing apparatus are that it be (1) usable in toxic and oxygen deficient atmospheres, (2) be activated rapidly, and (3) furnish a minimum of 1 hour of breathable oxygen even though the person wearing the apparatus is under considerable mental and physical stress and thus may require higher than normal amounts of oxygen. The device should have a 5-year shelf life and a 3-year service life and be light enough to be included as a part of the equipment normally carried by the worker, rather than requiring him to locate and rush to the nearest storage of breathers located at scattered locations throughout a work area. Desirably, the breather device should not be a filter respirator, should provide its own source of oxygen that will remove the carbon dioxide and water contained in exhaled breath and should furnish a breathable mixture of oxygen.